THE RELATIONSHIP BETWEEN MEASURES OF VOCAL FATIGUE METRICS AND PULMONARY FUNCTION TEST RESULTS

Transcription

1 THE RELATIONSHIP BETWEEN MEASURES OF VOCAL FATIGUE METRICS AND PULMONARY FUNCTION TEST RESULTS By Callan Aubrey Gavigan A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Communicative Sciences and Disorders Master of Arts 07

2 ABSTRACT THE RELATIONSHIP BETWEEN MEASURES OF VOCAL FATIGUE METRICS AND PULMONARY FUNCTION TEST RESULTS By Callan Aubrey Gavigan This research investigated the relationship between pulmonary function test metrics and vocal fatigue. Female participants underwent a two-day study, which included a screening, non-fatiguing and fatiguing tasks and pulmonary function testing. Subjective and objective measures indicating vocal fatigue were compared to pulmonary function measures. Subjective measures included participant s ratings of vocal fatigue on a 0-0 scale every 0 minutes throughout non-fatiguing and fatiguing tasks. Objective measures included variations of relative sound pressure level (SPL) and fundamental frequency (f 0 ) collected during both pre and post non-fatiguing and fatiguing tasks. Results indicated that the relationship between lung age and self-reported ratings of vocal fatigue were statistically significant (p<0.05). Variations in ΔSPL and f 0 that were collected during non-fatiguing and fatiguing tasks were both statistically significant (p<0.00) when compared to subjective ratings of vocal fatigue during the fatiguing task. Vocal tasks collected pre and post non-fatiguing and fatiguing tasks were not as sensitive to subjective ratings of vocal fatigue with ΔSPL compared to time (p<0.05) and f 0 compared to time (p<0.05). Data regarding pulmonary function and vocal fatigue call for continued study, as there are potential implications for use as a screening tool. Additionally, vocal measures collected during vocal fatiguing tasks are more indicative of vocal changes than pre and post non-fatiguing and fatiguing measures.

3 Copyright by CALLAN AUBREY GAVIGAN 07

4 I would like to dedicate this thesis to my family who has supported me throughout all my endeavors at Michigan State University. I couldn t have done it without you. iv

5 ACKNOWLEDGEMENTS I would like to acknowledge all persons involved in my experience at Michigan State University in the Communicative Sciences and Disorders master s program, thank you for your guidance and assistance in helping me to grow. To Dr. Eric Hunter, my thesis committee chair, thank you for being a source of positivity and support through this journey. Your willingness to give of your time was much appreciated. To Dr. Peter LaPine, my thesis committee member, thank you for your unwavering faith in my ability to succeed. To Dr. Jim Pivarnik, my thesis committee member, thank you for your understanding and flexibility. To all members of the Michigan State University Voice Biomechanics and Acoustics Laboratory, especially Emily Wilson and Russell Banks, thank you for your assistance conducting this experiment. To Pasquale Bottalico, thank you for always telling me when I was right and when I was wrong. Last but not least, to my classmates, friends and family, thank you, this wouldn t be possible without you. Thank you to the Department of Communicative Sciences and Disorders for awarding me a thesis scholarship, and providing me with the financial means to complete this project and share my results at conferences. Research was supported by the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health under Award Number R0DC035. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. v

6 TABLE OF CONTENTS LIST OF TABLES..... viii LIST OF FIGURES.... x KEY TO ABBREVIATONS..... xi CHAPTER : INTRODUCTION. Vocal Fatigue Symptoms... Previous Studies of Vocal Fatigue 3.3 The Gap. 7.4 Research Questions and Hypothesis. 9 CHAPTER : METHODS. Research Participants... Inclusion and Exclusion Criteria..3 Procedure 3.3. Day : Screening and Baseline Measures 3.3. Day : Vocal Loading Measures.. 4 CHAPTER 3: MEASURES Screening Tasks Independent Variables Dependent Variables Non-Fatiguing and Fatiguing Tasks... 9 CHAPTER 4: RESULTS.. 4. Participants Processing of Voice Recordings Statistical Method Subjective Vocal Fatigue Ratings Over Time Subjective Vocal Fatigue Ratings and Pulmonary Function Measures ΔSPL and f 0 in Vocal Tasks and Pulmonary Function Test Measures ΔSPL Over Time During Non-Fatiguing and Fatiguing Subjective Tasks f 0 Over Time During Non-Fatiguing and Fatiguing Subjective Tasks ΔSPL and f 0 Pre and Post Speech Tasks in Non-Fatiguing and Fatiguing Tasks. 34 CHAPTER 5: DISSCUSSIONS AND IMPLICATIONS Vocal Fatigue versus Time Vocal Fatigue versus Pulmonary Function Acoustic Measures versus Pulmonary Function Vocal Fatigue versus Acoustic Measures vi

7 CHAPTER 6: LIMITATIONS AND FUTURE DISCUSSIONS 4 CHAPTER 7: CONCLUSIONS APPENDICES.. 47 Appendix A. Consent Form.. 48 Appendix B. General Participant Information Appendix C. Vocal Health Survey Statistics Appendix D. Voice Handicap Index-0 (VHI-0) Appendix E. Voice-Related Quality of Life Measure (V-RQOL) Appendix F. Vocal Fatigue Index (VFI) Appendix G. Big Five Inventory -0 (BFI-0) Appendix H. Pulmonary Function Test Results Appendix I. Self-Reported Vocal Fatigue Ratings Appendix J. Acoustic Measures Results Appendix K. The Rainbow Passage.. 66 Appendix L. Day Protocol Instructions Appendix M. Day Protocol Instructions 73 Appendix N. IRB Approval Documents REFERENCES. 79 vii

8 LIST OF TABLES Table. A LME model fit by REML for the response variable self-reported vocal fatigue ratings (-) and as fixed factor the interactions of time and day Table. A LME model fit by REML for the response variable self-reported vocal fatigue ratings (-) and as fixed factors: () time, () FEV perc, (3) FVC perc, (3) PEF perc, (4) Lung age and (5) age... 7 Table 3. A LME model fit by REML for the response variable ΔSPL (db) and as fixed factors: () time, () FEV perc, (3) FVC perc, (3) PEF perc, (4) Lung age and (5) age. 9 Table 4. A LME model fit by REML the response variable f 0 (Hz) response variable ΔSPL (db) and as fixed factors: () time, () FEV perc, (3) FVC perc, (3) PEF perc, (4) Lung age and (5) age Table 5. A LME model fit by REML for the response variable ΔSPL (db) and as fixed factor the time, for Day and Day separately Table 6. A LME model fit by REML for the response variable ΔSPL (db) and as fixed factor self-reported vocal fatigue, for Day and Day separately Table 7. A LME model fit by REML for the response variable f 0 (Hz) and as fixed factor the time, for Day and Day separately. 3 Table 8. A LME model fit by REML for the response variable f 0 (Hz) and as fixed factor, self-reported vocal fatigue, for Day and Day separately... 3 Table 9. A LME model fit by REML for the response variable ΔSPL (db) and as fixed factor the time (Pre/Post task), for Day and Day separately Table 0. A LME model fit by REML for the response variable f 0 (Hz) and as fixed factor the time (Pre/Post task), for Day and Day separately Table A. Participants responses to general information and questions about voice... 5 Table A. Summary of participant responses collected from vocal health surveys conducted in the screening task of Day. 54 Table 3A. Preliminary analyses of a set of pulmonary function test results from collegeaged females in a Michigan State Kinesiology class collected prior to current study viii

9 Table 4A. Pulmonary function test results from this study compared to Occupational Safety and Health Standards (OSHA,07) Table 5A. Pulmonary function test results from this study for each participant.. 60 Table 6A. Self-Reported Vocal Fatigue Ratings from this study for each participant. 6 Table 7A. Acoustic measurements of ΔSPL (db) for each participant during My vocal fatigue level is statement. 63 Table 8A. Acoustic measurements of f 0 (Hz) for each participant during My vocal fatigue level is statement. 63 Table 9A. Acoustic measurements of ΔSPL (db) for each participant during vocal tasks (Diapix and Rainbow Passage). 64 Table 0A. Acoustic measurements of f 0 (Hz) for each participant during vocal tasks (Diapix and Rainbow Passage) Table A. Breathing screening form used to evaluate participants during Day.. 69 Table A. Hearing screening form used to evaluate participants during Day. 70 ix

10 LIST OF FIGURES Figure. Diagram of Flow: Day, showing the tasks participants shared in...4 Figure. Diagram of Flow: Day, showing the tasks participants engaged in 4 Figure 3. Self-reported vocal fatigue ratings over time in Day and in Day... 6 Figure 4. Self-reported vocal fatigue ratings by lung age Figure 5. Self-reported vocal fatigue ratings by lung age over time Figure 6. ΔSPL (db) in Non-Fatiguing task (Day ) and in Fatiguing Task (Day ) versus time and self-reported vocal fatigue ratings.. 3 Figure 7. f 0 (Hz) in Non-Fatiguing task (Day ) and in Fatiguing Task (Day ) versus time and self-reported vocal fatigue ratings.. 33 Figure 8. ΔSPL (db) and f 0 (Hz) in Day and in Day Pre and Post task.. 35 x

11 KEY TO ABBREVIATIONS BFI-0: Big Five Inventory-0 db: Decibel D: Day D: Day f 0 : Fundamental Frequency FEV: Forced Expiratory Volume in the st second FVC: Forced Vital capacity Hz: Hertz LME: Linear Mixed Effect PEF: Peak Expiratory Flow PFT: Pulmonary Function Test REML: Restricted Maximum Likelihood SPL: Sound Pressure Level V-RQOL: Voice-Related Quality of Life Measure VFI: Vocal Fatigue Index VHI-0: Voice Handicap Index-0 ΔSPL: Change in Sound Pressure Level xi

12 CHAPTER : INTRODUCTION There is a large sector, 5% or more of the working population in the United States, known as professional voice users who rely on voice use as an essential function of their job (National Center for Voice and Speech, 993). These occupational voice users (e.g., teachers, counselors, telephone workers) that depend on vocal endurance and vocal quality are impacted by voice disorders, vocal limitations, and vocal fatigue, more frequently than the general population (Titze, 997). The consequences implicated by voice problems, for example dysphonia (i.e. dysfunction in the ability to produce voice), are important and have a significant impact on job performance and quality of life (Verdolini & Ramig, 00). Solomon (008) discussed this The obvious impact of dysphonia on lost wages and productivity has motivated researchers in many countries to study occupational voice (p. 59). Teachers are one group of professional voice users with an elevated incidence of voice problems (Roy et al., 004), representing up to 76% of voice clinicians referrals (Morton & Watson, 998). One study suggests that these issues cost an estimated two billion United States Dollars annually (Verdolini & Ramig, 00). Smith, Kirchner, Taylor, Hoffman, and Lemke confirmed that within the teaching occupation females reported a higher rate of gender-related vocal symptoms (998). This is a similar trend with other high voice use occupations where women make up the primary workforce. Women may be nearly twice as likely to report a history of voice problems (Roy, Merrill, Gray, & Smith, 005), a finding that was consistent across the age span (Roy et al., 004).

13 . Vocal Fatigue Symptoms A common complaint in populations with voice problems, such as teachers, is vocal fatigue. Vocal fatigue has been identified as a multifaceted voice problem; its limitations can come from several different functional problems in physiological and anatomical systems (i.e. the muscular system, the nervous system and the respiratory system). This is discussed in greater detail by Solomon (008) and is referred to in several instances below. However, there is no universally accepted definition of vocal fatigue. Generally, vocal fatigue can be described as the worsening of one s voice with consistent use over an extended period of time, such as during the course of a day or over consecutive weeks. Parameters to measure the change in voice can include pitch, loudness, quality, etc. Verdolini, Rosen, Branski, Andrews, and the American Speech- Language-Hearing Association (006) defined vocal fatigue as a feeling of local tiredness and weak voice after a period of voice use. In a comprehensive review of current vocal fatigue research, Welham and Maclagan (003) stated while a link between vocal fatigue and other laryngeal pathologies is plausible, it is unclear whether vocal fatigue primarily contributes to, results from, or exists independently of other voice conditions (p. ). Nevertheless, while the underlying pathophysiology of vocal fatigue is unclear, previous research has identified several symptoms that generally accompany it. Solomon (008) identified these symptoms from the literature () increased vocal effort and discomfort, () reduced pitch range and flexibility, (3) reduced vocal projection or power, (4) reduced control of voice quality, (5) an increase in symptoms across the speaking day, and (6) improvement after resting (p ).

14 Supporting these symptoms and descriptions of vocal fatigue are different physiological and biomechanical mechanisms contributing to this multifaceted problem (Titze, 984 & 994). In one discussion of the physiological source, Titze (999) highlights two possible types of vocal fatigue: laryngeal muscle fatigue and laryngeal tissue fatigue. Welham and Maclagan (003) pointed out several different areas of research that have been conducted studying the symptoms of fatigue: neuromuscular fatigue, increased vocal fold viscosity, reduced blood circulation to the vocal folds, nonmuscular tissue strain, and respiratory muscle fatigue. Varying descriptions, a multitude of underlying factors and symptoms, and behavioral and individual differences have made it difficult to come to a consensus on vocal fatigue and its source. Research questions regarding fatigue have yet to be answered concretely by researchers indicating a need for continued exploration into this elaborate vocal problem. Additionally, Hunter, Tanner, and Smith (0) identified several components mentioned above which may contribute specifically to women s higher level of vulnerability to voice disorders: anatomical differences in the laryngeal systems, the impact of the endocrine system (e.g., hormones), non-laryngeal differences (e.g., pulmonary), and gender dependent nonphysiological and behavioral differences (e.g., stress reactions). These conclusions highlight a need to focus on the female population when researching voice problems.. Previous Studies of Vocal Fatigue Several studies have been conducted in an effort to induce fatigue for the purpose of studying the changes in voice post vocally fatiguing tasks and the potential underlying mechanisms. Teachers are often required to speak for long periods of time with few 3

15 breaks at an elevated voice level (e.g., high vocal load). Hunter and Titze (009) suggested an experimental model called a vocal loading task where reading or speaking is maintained over a prolonged period of time and can be used to induce vocal fatigue. In absence of a direct measure for vocal fatigue, combinations of subjective and objective measures have been used in previous research to investigate fatigue, which include: acoustic measures, aerodynamic measures, and self-ratings by subjects who indicated fatigue. As Boucher and Ayad (00) pointed out One can no more assess the validity of subjective scales than that of acoustic signs of vocal fatigue without some estimate of the physiological condition of fatigue as it relates to structures of the voice system (p. 34). Solomon (008) stated that individuals who experience vocal fatigue have an impression regarding its definition and how it feels. For example, Laukkanen and colleagues (004) used a questionnaire about throat and voice symptoms, given to participants to help assess the impact of a vocal loading task. However, these impressions are, as previously stated, subjective; and, while they have clinical relevance for treatment, verification of the presence of vocal fatigue cannot be determined using only this measure. The complexity of evaluating fatigue requires multiple supports to accurately identify its existence. Therefore, in an attempt to quantify self-reports of vocal fatigue and other subjective measures, assessment of vocal fatigue has been investigated with the implication of acoustic and physiological measurements. Laukkanen, Ilomäki, Leppänen, and Vilkman (008) studied 79 female primary school teachers using a mixture of acoustic measures and self-reports of vocal fatigue. They analyzed the outcomes of female teachers prior to and following their typical workday and analyzed their speaking samples for fundamental frequency (f 0 ), sound 4

16 pressure level (SPL), phonation type reflecting alpha ratio, and perturbation values (i.e. jitter and shimmer). The authors concluded that there was an increased value in the acoustic measures stated above evident after a working day; hence, the teacher s voices were more dysphonic. In another study of vocal fatigue, Vilkman, Lauri, Alku, Sala, and Sihvo (999) also used acoustic measures as well as subglottal pressure and glottal flow waveform parameters. Again, consistent with other research findings, all acoustic measures increased after a period of vocal fatigue. The literature reflects that vocal fatigue results in acoustic changes but there is disagreement regarding what parameters should be used for assessment, as evidenced by the variety of measures mentioned in the studies above. However, besides these observable acoustic changes there may be a physiologic change in the vocal mechanisms that alter how people sound. Other attempts to quantify the presence of vocal fatigue have implicated physiologic measures. Boucher, Ahmarani, and Ayad (006) used intramuscular electromyograghy (EMG) spectral compression to observe whether laryngeal muscles fatigued as a result of prolonged vocal effort. Spectral compression was evidenced for all subjects proving that it is a reliable measure for a physiologic feature, muscle changes, and indicative of excessive vocalization. Boucher and Ayad (00) conducted a threepart study, building on their research in 006, in an attempt to define the physiologic features of vocal fatigue. In the study, electromyographic (EMG) observations demonstrated fatigue of laryngeal muscle fatigue after a vocal loading task with evidence for signs of tremor, which was indicative of increased vocal effort. However, after systematic vocal loading and confirmation of muscle fatigue there were no relationships with acoustic parameters. This poses the question whether the acoustic parameters 5

17 currently being used to assess vocal fatigue are an accurate representation of laryngeal muscle responses. Putting all these measures together, researchers have still struggled to identify decisive information about this vocal problem. As stated by Hunter and Titze (009), Buekers (998) found that vocal fatigue could not be conclusively identified using self-ratings of pain and fatigue, electroglottography (EGG), standard acoustic metrics (i.e., the Multi-Dimensional Voice Program), or pitch/loudness measures (monitored throughout the day on a subset of subjects) (p. 3). Presently, there is clear evidence that none of these measures alone are able to concretely identify vocal fatigue in an individual. While a person can indicate subjectively where they are feeling the effects of fatigue, this does not offer a standard measure among all individuals. Acoustic measures do show statistical correlation with subjective measures of fatigue, but varying acoustic parameters are used without agreement on the best one. Simultaneously, acoustic measures do not always correlate with physiologic measures that have been shown to identify fatigue. Research across the field of voice identifies a multitude of potential physiologic features that may be impacting vocal fatigue, with some causes having small amounts of evidential support and others being speculative. Solomon, Glaze, Arnold, and Mersbergen (003) stated that there has been an increase in research to assist in the development of methods and procedures that detect important changes in vocal function after vocally fatiguing tasks. These have included questionnaires, acoustic measures, laryngeal videostroboscopy, and aerodynamic measures (p. 3-3). To this end, a multifaceted problem like vocal fatigue requires exploration into several possible areas of human communication that it impacts. There is clear 6

18 identification of a portion of the population that is most susceptible to fatigue and some of the evidenced symptoms. Additionally, defining and implementing the necessary measures and systems tied to fatigue has continued to improve. However, there is still a void regarding some of the physiologic and anatomical factors that could be contributing to vocal fatigue. This research could help to fill in some of the gaps in the current literature to give a more complete picture of the problem of vocal fatigue..3 The Gap Of all the plausible physiological systems that could contribute to vocal fatigue, little research has been done to investigate the significance of respiratory support, speech breathing and proper breath support and what its potential role may be. The general mechanism of the speech system can be thought of in three subsystems, though not independent: the lungs, the vocal folds and the vocal tract. The lungs act as the pump of the system and are needed to provide airflow to vibrate the vocal folds. This is necessary to produce energy for the system and fuel the voice. Airflow from the lungs comes up through the vocal folds causing a wave-like motion in the vocal folds producing vibration and thus voicing. Next, the vocal tract makeup of the tongue, palate, cheek and lips shape and filter the frequencies that create to make specific phonemes. These three components have to work together harmoniously to facilitate the coordination of the speech processes respiration, phonation, articulation and resonance. A more detailed description of voice production can be found elsewhere (Titze, 994). As explained above, the coordination of respiratory control and breath support in the lungs is key for subglottal air pressure and airflow necessary to phonate. Past 7

19 researchers, (Welhman & Maclagan, 003), have discussed the contribution of respiratory muscle fatigue in vocal fatigue. They commented, Titze (984 & 994) suggests that respiratory muscle fatigue, resulting in reduced subglottal pressure capacity, may be a further contributing mechanism in the onset of vocal fatigue (003, p. 4). However, simultaneous functioning of the laryngeal and respiratory mechanisms is needed to produce adequate vocal intensity and the voice-voiceless contrast of consonants in the English Language. If there is poor breath support then laryngeal compensation is necessary; and, inadequate breath support initially will produce suboptimal vocal fold vibration causing fatigue to occur at a higher rate. Stathopoulos and Sapienza (993) stated Respiratory results indicate that tracheal pressure, percent rib cage contribution, lung volume, and rib cage volume initiations are higher, and lung and rib cage volume excursions are larger when higher vocal intensity levels are produced (p. 64). While clinically discussed, limited studies have touched on the adequate breath support that supply the energy needed for good vocal fold vibration. A general lack of breath support could be caused by lung function problems, such as disease or illness, or smaller than average lung size, which can be different among individuals, and may lead to vocal dysfunction. Iwarsson, Thomasson, and Sundberg (998) studied the impacts of lung volumes relative to glottal voice source characteristics and definitively showed that respiration affects phonation. We found higher subglottal pressure, greater flow amplitude, a lower closed quotient, greater glottal leakage, and greater relative estimated glottal area at high as compared to low LV (lung volume) (Iwarsson et al., 998, p. 430). Hunter and colleagues hypothesized something similar to this potential relationship within females, who are at greater risk for voice problems. 8

20 Hunter et al. (0) stated To maintain voicing with insufficient airflow, these women would have to compensate with increase laryngeal adduction, creating more contact force per unit area on the medical edges of the folds, which is ultimately a less healthy vocalization style (p. 3). Further research has indicated that healthy lung function and capacity is associated with reduced vocal complaints. For example, Maxfield, Hunter, and Graetzer (06) collected data from teachers and showed that the Vocal Fatigue Index (VFI) (Nanjundeswaran, Jacobson, Gartner-Schmidt, & Verdolini Abbott, 05) was a predictor to several spirometry measures in female teachers. While this study showed a moderate relationship between spirometry and vocal fatigue complaints, the later was only quantified by response to questions and not from actual changes (real or perceived) of vocal fatigue due to vocal loading..4 Research Questions and Hypothesis This study builds on the concept that breath support may affect vocal fatigue. Previous studies have implied a connection between lung function and breath support as well as breath support and vocal fatigue. Pulmonary function tests (PFTs) may give insights into a connection between lung volumes/function and vocal fatigue. Therefore, the research question for the study is as follows: To what degree (i.e., the magnitude of correlation) do PFT results relate to the extent of vocal fatigue from a fatiguing task? In addressing this question, it was hypothesized that otherwise healthy individuals with lower PFT results indicating smaller lung volumes or lung utilization will have greater vocal fatigue (shown through measures of vocal effort and quality) compared to individuals with higher PFT results indicating average or larger than average lung 9

21 volumes. Values from PFT results were compared against normative values of age, race, sex, and body size for each individual participant. To test the hypothesis and answer the question above, research participants took part in a vocal loading experiment. Within the experiment, the extent of vocal fatigue from the participants voice samples during a vocal loading task were quantified via subject response and acoustic analysis and then compared to PFT results. 0

22 CHAPTER : METHODS This study addressed the research question by having participants complete a vocal fatiguing task and a PFT. Objective and subjective measures related to vocal fatigue were used to compare against metrics of pulmonary function tests. Each measure introduced in the methods will be discussed in detail in the following chapter. To be eligible, participants underwent several screening and baseline measures, including a videoendoscopic exam. The Michigan State University Institutional Review Board approved study procedures outlined below. Written informed consent was obtained from each participant prior to beginning the study.. Research Participants College-aged female participants were recruited for the study. This was due to the high propensity of vocal fatigue among women compared to men as reported in the literature, and by the results of Maxfield et al. (06) where vocal fatigue complaints among female teachers significantly correlated to PFT metrics. There was no affect found among the male teachers in the study. The goal was to have 0 participants complete the study. This number was based on the previous results from studies done by Bottalico (06) and Cutiva, Puglisi, Astolfi, and Carullo (07) from which two different power analyses were calculated based on db SPL of teacher s voices who were experiencing vocal fatigue. A balanced one-way analysis of variance power calculation showed that with 0 subjects a statistical power of 80% and a significance level of p < 0.0 was reached using both studies. The outcome used was the standard deviation f 0. Therefore, a

23 total of ten college-aged females ranging from 8-40 years of age, participated in the entire study.. Inclusion and Exclusion Criteria Only participants with no self-reported past vocal, speech, pulmonary or hearing problems that required intervention of a speech-language pathologist or other physician were accepted into the study. Vocally and athletically trained individuals, at the college level, and non-native English speakers were also excluded. Study participants were required to meet inclusion and exclusion criteria from the Day (D) screening. Initially, participants were screened via a rigid oral endoscopic exam to ensure there are no apparent laryngeal abnormalities. Additionally, a recording of standard vocal tasks, breathing screening and hearing screening were conducted. If participants failed any of these three screenings they were excluded. Participants were asked about allergies and over the counter or prescribed medications, which may affect the respiratory system or airway. Common antihistamines for allergies can have a drying effect on the vocal folds or slightly adjust vocal fold quality, which was important to note. This included abnormalities such as a participant present with allergies, medications affecting vocal hydration, history of gastroesophageal reflux disease (GERD), benign lesions and upper respiratory tract infections. However, participants who answered yes to any of these questions were not excluded from the study. If after day one, any screening results excluded a participant from the study they were given appropriate compensation but not asked not to return for the remainder of the study. New participants

24 were recruited and screened until a total of 0 participants successfully completed the study..3 Procedure The study was split into two days for each subject. Below is a short summary of each day. The goal of participation was to obtain PFT metrics that could be compared to subjective and objective measures of vocal fatigue. This included self-ratings of vocal fatigue, SPL and f 0 based on measures extracted from recordings as detailed below..3. Day : Screening and Baseline Measures On the initial day, participants completed a consent form, a baseline vocal recording, standard vocal health questionnaires, an endoscopic exam, a hearing screening and a breathing screening. After these screening and baseline procedures, participants engaged in a non-fatiguing task, where subjective fatigue ratings were gathered as well as pre and post vocal recordings, and a PFT. After given appropriate information including risks and benefits of the study participants provided written consent to begin. An endoscopic exam was performed on all participants to verify vocal fold motility and lack of apparent laryngeal abnormalities. Participants completed a set of vocal and speech recordings as a baseline measure prior to the non-fatiguing task. They then began the non-fatiguing task for 30 minutes where the participant regularly rated their vocal fatigue level. During the non-fatiguing task, participants completed a breathing screening, hearing screening, and electronic vocal health surveys. These tasks were conducted within the non-fatiguing task since they only 3

25 required a minimal amount of speaking by the participants, not enough to induce vocal fatigue, and decreased the overall run time of the study. The participants then completed a second set of vocal and speech recordings at the end of the non-fatiguing task. A PFT was then conducted with the use of a spirometer to complete the participation of D. Consent Screening Tasks Vocal Measures Non- Fatiguing Task Vocal Measures Pulmonary Function Test Figure. Diagram of Flow: Day, showing the tasks participants shared in..3. Day : Vocal Loading Measures On Day (D) of the study, participants again completed a PFT as well as the same set of vocal and speech recordings as done in D. Next the participants read aloud in a vocal loading task for the same duration of time as the non-fatiguing task (30- mintues) and regularly rated their vocal fatigue level throughout. After the fatiguing task, participants again performed the same short vocal recordings as before followed by a PFT. Vocal Measures Fatiguing Task Vocal Measures Pulmonary Function Test Figure. Diagram of Flow: Day, showing the tasks participants engaged in. 4

26 CHAPTER 3: MEASURES To reiterate, the research question being investigated was the relationship between PFT results and measures of vocal fatigue. In order to understand this possible connection, objective measures from vocal recordings and subjective measures were quantified for comparison with spirometry metrics. The objective measures pulled from vocal recordings were collected pre and post non-fatiguing and fatiguing tasks and included f 0 and variations of SPL. Subjective measures were collected during nonfatiguing and fatiguing tasks and were participant s response to the statement: My vocal fatigue level is. (on a 0 to 0 scale). Thus, the independent variable within this research study was the variation of pulmonary function results (lung volumes and capacities) and the dependent variable being studied was the measure of change that was observed in subjective and objective tasks that represent fatigue. 3. Screening Tasks While not specifically part of the research question, the participants filled out electronic vocal health related questionnaires. The survey responses were collected via Qualtrics Survey Software and included: the Voice Handicap Index-0 (VHI-0), the Voice-Related Quality of Life Measure (V-RQOL), the VFI and the Big Five Inventory - 0 (BFI-0) (see Appendices). Additionally, participants underwent a endoscopic screening exam, a breathing screening and a hearing screening. A rigid oral endoscopy was used to identify any anatomical or laryngeal anomalies that could potentially affect the study participants. A rigid endoscope was 5

27 coupled with a digital camera and stroboscopic light source to view the larynx and vocal folds. All equipment was disinfected and sterilized with.4 percent Gluteraldahyde prior to each use. A licensed and clinically certified speech-language pathologist supervised the experimenter performing the examination. A general respiratory assessment was given to determine different types of breathing that participants might exhibit and whether their participation was appropriate for the study. The breathing types assessed included: () diaphragmatic (an inhale pushes the abdomen outwards); () thoracic (during inhale the chest expands anteriorly to accommodate the air that fills the lungs); (3) clavicular (during inhale the clavicle goes up to accommodate the air that has been sucked into the upper part of the lungs); (4) paradoxical (the chest compresses on the inhale rather than expands and vice versa). Participants who exhibited clavicular or paradoxical breathing patterns were excluded from the study because of the abnormality of these breathing types. The type of respiration cycle in the absence of speech, which can be oral-oral, nasal-nasal, and oralnasal, were marked. Coordination of respiration and voice was the final component of the breathing screening which was marked adequate or inadequate based on the participants performance. Lack of coordination also excluded participants from the study. A brief hearing screening was completed to ensure that participants hearing was adequate for inclusion in the study. A bilateral hearing screening was conduced at 5 db at frequencies of 5 Hz, 50 Hz, 500 Hz,,000 Hz,,000 Hz, 4,000 Hz and 8,000 Hz. If participants failed to respond to tones at any of these frequencies they were excluded from the study. 6

28 3. Independent Variables A PFT was conducted with the use of an electronic CareFusion microlab spirometer and software program (SpiroUSB Model BZG, Micro Direct; Lewiston, ME) to assess, collect and record data about participant s lung function. This was done on the initial and second days of the study. To obtain accurate standardization results in post-test analysis participant s height, age, smoking history, gender, and race were recorded within the system prior to the test. Standards by Wang, Dockery, Wypij, Fay, and Ferris (993) and Hankinson, Odencrantz, and Fedan (999) were used to determine the range of percentage of normal for pulmonary function measures. For the duration of the test, participants were seated in an upright position and asked to wear a nose clip. The experimenter provided a demonstration for participants and then asked them to perform a trial to confirm correct execution. Participants were provided the following instructions: Please inhale as much and as deeply as you can as quickly as you can. Then, exhale as fast as you can pushing all the air out of your lungs. Do not pause between the inhalation and exhalation. Feel free to use the rest of your body to more as much air as possible. The CareFusion program required three attempts of results within 5% of each other to confirm accurate PFT results from the participant. If participants were unable to produce three attempts within 5% percent of each other after six trials, the next three closets attempts to the target were selected for analysis. The experimenter provided verbal motivation and coaching through encouraging phrases as necessary to elicit the best possible effort to produce accurate measurements of the PFT. The measures collected included, but were not limited to, forced vital capacity (FVC), forced expiratory volume in the first second (FEV), peak expiratory flow (PEF) 7

29 and predicted lung age. FVC, measured in liters, is the lung complete capacity that can be forcibly exhaled by someone after his or her deepest breath possible. FEV, measured in liters, is the forced expiratory volume in st second of exhalation. PEF, measured in liters per second, is the maximum flow during expiration when produced with force. Predicted lung age, measured in years, is the based on a participant s lung function as measured during a pulmonary function test. An equation is used to calculate predicted lung age and often involves FEV compared to norms for the individual. These specific measures have been chosen for review based on results from Maxfield et al. (06), which showed correlation between spirometery measures and participants responses in the vocal fatigue index. Subjects were allowed to view spirometery results following their PFTs. They were not informed of the hypothesis of the study at any point during the experiment to avoid any potential bias of their self-rated responses. 3.3 Dependent Variables Subjective Fatigue Rating: Participants self-reported perception of their current vocal fatigue level was indicated via verbal response on a scale from zero to 0. They were instructed that a rating of zero indicated no sensation of vocal fatigue while a rating of 0 indicated the greatest level of vocal fatigue. The rating was elicited via the statement My vocal fatigue level is throughout non-fatiguing and fatiguing tasks every 0 minutes during D and D of the study. Objective Voice Metrics: Voice metrics were obtained from participants voice recordings taken before and after the non-fatiguing and fatiguing task as well as from the self-reported vocal fatigue ratings. Participants were asked to orally describe a picture 8

30 (Diapix) and to read aloud a standard passage (The Rainbow Passage, Appendix K). In the Diapix task, participants were given a picture scene and asked to describe its image to an unfamiliar listener for 40 seconds (Baker & Hazan, 0). For the reading passage, participants were asked to read first paragraph of The Rainbow Passage. They were recorded with a head mounted microphone (Glottal Enterprises, M80) and a portable digital recorder (Roland). From these recordings, objective vocal measures were calculated, namely f 0 and SPL. A participant s vocal pitch is associated with the measure f 0, measured in hertz (Hz), and represents the number of vocal fold collisions per second (Hunter & Titze, 00). SPL is a ratio of the sound pressure and a reference level, usually the human threshold of hearing, and is a physical reference for a participant s vocal intensity, which is measured in decibels (db). An increase in SPL can imply an rise in vocal fold intensity or larger vocal fold stress (Hunter & Titze, 00). 3.4 Non-Fatiguing and Fatiguing Tasks A non-fatiguing task was completed during D and used as a control for participants to compare to their fatiguing task on D. In both tasks, participants were asked to attend to the software program for the same 30-minute period of time. During the control vocal loading task, participants were asked to remain essentially silent, except to respond with one to two word answers, while completing a breathing screening and a hearing screening. Additionally, at four different time points (0 minutes, 0 minutes, 0 minutes and 30 minutes) in the non-fatiguing participants were asked to verbally respond to the subjective statement My vocal fatigue level is. 9

31 As an experimental task to compare to the non-fatiguing task, all participants completed a vocal loading test using the lingwaves program (Version 3.0; Wevosys, 04). Prior to the start of the program, participants were given instructions to ensure their comprehension of the task as well as reading material for the test. For this particular experiment Charlotte s Web by E.B. White (0) was selected as the reading material because of its popularity in classic fiction, elementary reading level and opportunity to use increased prosody when reading the text. The experimental vocal loading task required subjects to complete the protocol listed in the following paragraph. As stated, the lingwaves system was used to conduct the vocal fatiguing task and collect data, specifically in vocal load test module setting. The system provided a very clear module for participants to follow in an attempt to induce vocal fatigue. During the 30-minute test db SPL goals, vocal intensity measures, alternated between 66 db and 7 db, every five minutes, based on ISO 99 standard of normal and raised speech level. This change in db SPL throughout the task simulated typical speech patterns throughout the day, especially that of teachers. Individuals have to alter their vocal intensity in conjunction with social situations, distance between speakers and background noise that might occur within an environment. In a sound-treated booth, the participants were seated directly in from of a computer screen with the lingwaves system and reading material on two separate monitors. The mouth-to-microphone distance relative to the sound level meter was placed 50 centimeters away the participants mouth. Throughout the vocal loading test, the program indicated to the participants with a large arrow if they fell below the desired db SPL goal. Participants read the provided text given the following instructions: Please read the provided material as if you were 0

32 speaking to a classroom of students. Attempt to make your voice animated and engaging to your listeners while reading at the level dictated by the program. If you fall below the desired speaking level, a large blue arrow will appear on the screen indicating that you need to raise your voice. Please increase your speaking volume until the arrow disappears. Be aware that throughout the test the required volume level will alternate. Additionally, in exact comparison to the non-fatiguing task, at four different time points (0 minutes, 0 minutes, 0 minutes and 30 minutes) in the vocal loading task participants verbally responded to the subjective statement My vocal fatigue level is. So after one complete db SPL goal cycle, which is five minutes at a normal speaking level (66 db) and five minutes at a raised speaking level (7 db), vocal fatigue ratings were assessed. This was done so the vocal load between each cycle was consistent. Self-reported vocal fatigue responses were also the primary fatigue indicator in analysis.

33 CHAPTER 4: RESULTS Using the above protocol, descriptive and inferential statistical methods were performed. Specifically, measures from the PFTs and the prolonged speaking protocol (fatiguing test) and its counter (non-fatiguing test) were used in this analysis. Parametric but robust non-normal distributions (semiparametric) tests were used. To look directly at the hypothesis, inferential statistical analysis was conducted using Linear Mixed-Effects (LME) models. Outcome measures included self-reported ratings of vocal fatigue and acoustic measures of ΔSPL and f 0. The results below were outlined in the following order. To begin, self-reported vocal fatigue ratings over time versus D and D were investigated. This provided verification that participants did perceive vocal fatigue in the fatiguing task. Self-reported vocal fatigue ratings were then compared to pulmonary function measures to explore a potential connection. Predicted lung age was found to have a statistically significant relationship with vocal fatigue. This was then researched further by comparing different predicted lung ages of participants to their reports of vocal fatigue over time. Next, acoustic measures were compared with other measures collected throughout the study. ΔSPL and f 0 in vocal tasks versus pulmonary function test measures were studied first. Then, ΔSPL and f 0 in D and in D versus time and self-reported vocal fatigue ratings were the second areas considered. Both of these measures showed statistically significant relationships within the non-fatiguing and fatiguing tasks. Finally, speech tasks completed pre and post non-fatiguing and fatiguing tasks were compared to ΔSPL and f 0.

34 In each results section below the model is described and more specifics of the factors used are provided. It should be noted that Dr. Pasquale Bottalico provided his expert advice and assistance to gain a better understanding of the statistical analysis that should be conducted. For clarification of the hypothesis and to determine if an inverse relationship existed between vocal fatigue and pulmonary function, the following measures were included in statistical analysis: Subjective measures (self-reported ratings of vocal fatigue) Acoustic measures (ΔSPL and f 0 ) Pulmonary Function measures (FVC, FEV, PEF and predicted lung age) Time of non-fatiguing or fatiguing task 4. Participants In total participants were run through the aforementioned protocol for the experiment. Two of those participants were excluded in the final statistical analysis. One participant failed to pass a hearing screening conducted on Day of the study. The other participant dropped a piece of equipment during the study thus affecting the recording and making data unusable. Of the 0 participants included in the final analysis age range was from 9-8 years with a mean age of 3.8 years. Participants responded to general questions regarding voice and specific questions to fulfill inclusion/exclusion (Appendix B). 3

35 4. Processing of Voice Recordings From the vocal task recordings (Diapix, Rainbow and vocal fatigue response statement My vocal fatigue level is ) time history estimates of f 0 and relative db SPL were estimated every 5 msec using custom laboratory scripts in Matlab06a. From the time history values, averages were calculated and used in statistical analysis. Additionally, a parameter termed ΔSPL was calculated as a within-participant centering (overall mean of a subject from all recordings subtracted by the individual task mean) in order to evaluate the variation in the participant s vocal behavior in the different conditions from the mean vocal behavior. 4.3 Statistical Method Statistical analysis was conducted using R version 3.. (RDevelopment, 03). Linear Mixed-Effects (LME) models were fit by restricted maximum likelihood (REML). Random effects terms were chosen on the basis of variance explained in the model. These were selected on the basis of the Akaike information criterion (Akaike, 998) (the model with the lowest value being preferred) and the results of likelihood ratio tests (a significant result indicating that the more complex of the two nested models in the comparison is preferred) and were conducted using lme4 and lmertest packages. The p values for these tests were adjusted using the default single-step method (Hothorn, Bretz, & Westfall, 008). The LME output included estimates of the fixed effects coefficients, the standard error associated with the estimate, the degrees of freedom, df, the test statistic, t, and the p value. The Satterthwaite method was used to approximate degrees of freedom and calculate p values. 4

36 4.4 Subjective Vocal Fatigue Ratings Over Time The self-reported vocal fatigue ratings (My vocal fatigue level is ) change over the duration of the non-fatiguing and fatiguing tasks and are shown in Figure 3. Here the slope of the self-reported vocal fatigue rating (range 0-0) per minute was in D and 0.6 in D. This was calculated using a LME model with the response variable as subjective vocal fatigue (-) and as fixed factor the interactions between day and time. The random effect for this model was the participant. Other potential interactions were excluded after likelihood-ratio tests indicated that their inclusion did not improve the model fit (p > 0.). The model results are presented in Table. Table. A LME model fit by REML for the response variable self-reported vocal fatigue ratings (-) and as fixed factor the interactions of time and day. Fixed factors Estimate Std. Error df t p (Intercept) <0.00*** Time:Day <0.00*** Time:Day <0.00*** Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. 5

37 Figure 3. Self-reported vocal fatigue ratings over time in Day and in Day. 4.5 Subjective Vocal Fatigue Ratings and Pulmonary Function Measures The effects of pulmonary function on self-reported vocal fatigue ratings (My vocal fatigue level is ) during the fatiguing task on D are presented in Table. As would be expected, an association between self-reported vocal fatigue ratings and time was confirmed. But of the PFT metrics, only the relationship between estimated lung age and self-reported vocal fatigue ratings was statistically significant (p < 0.05). This was conducted with a LME model with the response variable as self-reported vocal fatigue ratings (-) and as fixed factors: () time, () FEV percentage, (3) FVC percentage, (3) PEF percentage, (4) Lung age and (5) age. The random effect for this model was the subject. To illustrate these effects, Figure 4 shows the average self-reported vocal fatigue 6

38 ratings by lung age while Figure 5 displays the reported the slope of self-reported vocal fatigue ratings over the time by lung age. Table. A LME model fit by REML for the response variable self-reported vocal fatigue ratings (-) and as fixed factors: () time, () FEV perc, (3) FVC perc, (3) PEF perc, (4) Lung age and (5) age. Fixed factors Estimate Std. Error df t p (Intercept) Time <0.00*** FEV_perc FVC_perc PEF_perc Lung age * Age Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. Figure 4. Self-reported vocal fatigue ratings by lung age. 7

39 Figure 5. Self-reported vocal fatigue ratings by lung age over time. 4.6 ΔSPL and f 0 in Vocal Tasks and Pulmonary Function Test Measures The effects of pulmonary function on variations in ΔSPL during vocal tasks (Diapix and Rainbow Passage) are presented in Table 3. An association between PFT metrics and time was confirmed however none of the other relationships between ΔSPL and PFT measures were significant. This was conducted with a LME model with the response variable as ΔSPL (db) and as fixed factors: () time, () FEV percentage, (3) FVC percentage, (3) PEF percentage, (4) Lung age and (5) age. The random effect for this model was the subject. The effects of pulmonary function on f 0 during vocal tasks are presented in Table 4. An association between PFT metrics and time was confirmed (p < 0.00) with relationships between PEF and lung age also showing significance (p < 0.). This was 8

40 conducted with a LME model with the response variable as variations in f 0 (Hz) and as fixed factors: () time, () FEV percentage, (3) FVC percentage, (3) PEF percentage, (4) Lung age and (5) age. The random effect for this model was the subject. Table 3. A LME model fit by REML for the response variable ΔSPL (db) and as fixed factors: () time, () FEV perc, (3) FVC perc, (3) PEF perc, (4) Lung age and (5) age. Fixed factors Estimate Std. Error df t p (Intercept) Time <0.00*** FEV_perc FVC_perc PEF_perc Lung age Age Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. Table 4. A LME model fit by REML the response variable f 0 (Hz) and as fixed factors: () time, () FEV perc, (3) FVC perc, (3) PEF perc, (4) Lung age and (5) age. Fixed factors Estimate Std. Error df t p (Intercept) <0.00*** Time <0.00*** FEV_perc FVC_perc PEF_perc Lung age Age Signif. Codes: *** <0.00 ** <0.0 * <0.05. < ΔSPL Over Time During Non-Fatiguing and Fatiguing Subjective Tasks Over the course of the fatigue tasks, participants changed how they spoke (Figure 6). The linear model was ideal for variations in SPL over time completed during subjective vocal fatigue task (My vocal fatigue level is ) for D. Alternatively, the quadratic model was ideal for variation in SPL over time completed in the same task for D. This was computed with LME models with the response variable as ΔSPL (db) and as fixed factor the time for D and D separately. The random effect for the model was the participant. Null, linear and quadratic models were compared for enhanced 9

41 understanding of the relationship between ΔSPL and time. Between them the simplest was chosen after likelihood-ratio tests indicated that the inclusion of more complex ones did not improve the model fit (p > 0.). Table 5 indicates the results from this model. For D the variation in ΔSPL was not associated to self-reported vocal fatigue and a null model was preferred. In D the relationship between ΔSPL and vocal fatigue was quadratic. Figure 6 shows associations of both models. This was calculated with a LME model with the response variable as ΔSPL and as fixed factor self-reported vocal fatigue for D and D separately. The random effect for the model was the participant. Table 6 indicates the results from this model. Table 5. A LME model fit by REML for the response variable ΔSPL (db) and as fixed factor the time, for Day and Day separately. Day Std. Fixed factors Estimate Error df t p (Intercept) Time * (Intercept) Time <0.00*** Time <0.00*** Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. Table 6. A LME model fit by REML for the response variable ΔSPL (db) and as fixed factor self-reported vocal fatigue, for Day and Day separately. Day Std. Fixed factors Estimate Error df t p (Intercept) Vocal fatigue <0.00*** Vocal fatigue <0.00*** Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. 30

42 5.0 Day 5.0 Day.5.5 ΔSPL [db] 0.0 ΔSPL [db] Time [min] Self-reported vocal fatigue [-] 5.0 Day 5.0 Day.5.5 ΔSPL [db] 0.0 ΔSPL [db] Time [min] Self-reported vocal fatigue [-] Figure 6. ΔSPL (db) in Non-Fatiguing task (Day ) and in Fatiguing Task (Day ) versus time and self-reported vocal fatigue ratings. 4.8 f 0 Over Time During Non-Fatiguing and Fatiguing Subjective Tasks Over the course of the fatigue tasks, participants changed their pitch (Figure 7). The linear model was ideal for f 0 over time completed during subjective vocal fatigue task (My vocal fatigue level is ) for Day. Alternatively, the quadratic model was ideal for f 0 over time completed in the same task for D. This was calculated with LME 3

43 models with the response variable as f 0 and as fixed factor the time for D and D separately. The random effect for this model was the participant. Null, linear and quadratic models were compared for enhanced understanding of the relationship between f 0 and time. Between them the simplest was chosen after likelihood-ratio tests indicated that the inclusion of more complex ones did not improve the model fit (p > 0.). Table 7 indicates the results from this model. For D the variation in f 0 was not associated to self-reported vocal fatigue as the null model was preferred. In D the relationship between f 0 and vocal fatigue is quadratic. Figure 7 shows associations of both models. LME models were run with the response variable f 0 and as fixed factor self-reported vocal fatigue for D and D separately. The random effect for the model was the participant. Table 8 indicates the results from this model. Table 7. A LME model fit by REML for the response variable f 0 (Hz) and as fixed factor the time, for Day and Day separately. Day Std. Fixed factors Estimate Error df t p (Intercept) <0.00*** Time (Intercept) <0.00*** Time <0.00*** Time ** Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. Table 8. A LME model fit by REML for the response variable f 0 (Hz) and as fixed factor, self-reported vocal fatigue, for Day and Day separately. Day Std. Fixed factors Estimate Error df t p (Intercept) <0.00*** Vocal fatigue <0.00*** Vocal fatigue ** Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. 3

44 75 Day 75 Day f0 [Hz] 5 f0 [Hz] Time [min] Self-reported vocal fatigue [-] 75 Day 75 Day f0 [Hz] 5 f0 [Hz] Time [min] Self-reported vocal fatigue [-] Figure 7. f 0 (Hz) in Non-Fatiguing task (Day ) and in Fatiguing Task (Day ) versus time and self-reported vocal fatigue ratings. 33

45 4.9 ΔSPL and f 0 Pre and Post Speech Tasks in Non-Fatiguing and Fatiguing Tasks The relationship between the variation in ΔSPL and f 0 before and after speech tasks (Diapix and Rainbow Passage) in D and D is shown in Figure 8. There was an increase in SPL of 0.79 db comparing before and after the task in D, while the increase of 0.85 db obtained during D was non statistically significant. There was a nonsignificant increase in f 0 comparing before and after the task in D, while the increase of 6.4 Hz obtained during D was statistically significant (Figure 8). This was conducted with LME models with the response variable as ΔSPL and as fixed factor the time (Pre/Post task) for D and D separately. The random effect for this model was the participant. Model results are shown in Table 9 for ΔSPL and in Table 0 for f 0. Table 9. A LME model fit by REML for the response variable ΔSPL (db) and as fixed factor the time (Pre/Post task), for Day and Day separately. Day Std. Fixed factors Estimate Error df t p (Intercept) Time Post * (Intercept) Time Post Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. Table 0. A LME model fit by REML for the response variable f 0 (Hz) and as fixed factor the time (Pre/Post task), for Day and Day separately. Day Fixed factors Estimate Std. Error df t p (Intercept) <0.00*** Time Post (Intercept) <0.00*** Time Post * Signif. Codes: *** <0.00 ** <0.0 * <0.05. <0. 34

46 0.5 ΔSPL [db] Pre Post Pre Post prepost 5 f0 [Hz] 0 day 05 Pre Post Pre Post prepost Figure 8. ΔSPL (db) and f 0 (Hz) in Day and in Day Pre and Post task. 35

47 CHAPTER 5: DISCUSSIONS AND IMPLICATIONS 5. Vocal Fatigue versus Time As expected, participants were aware of the effects of the prolonged reading task (vocal fatigue) and their subjective rating increased over time during the task. This awareness was quantified by a statistically significant positive relationship when comparing self-reported vocal fatigue ratings and reading time during the task on D. During the non-fatiguing task on D there was a also a statistically significant negative relationship between self-reported vocal fatigue ratings and time. This may have been due to initial anxiety of the participant when they started the study and became more relaxed and familiarized with the investigator. Most importantly these results confirmed that the participants felt that the reading task did induce vocal fatigue. Clinically, individuals who have incurred vocal fold trauma either from a surgery or excessive voice use are the population for which vocal rest is generally recommended. From the study results though it can be concluded that even for individuals with no vocal abnormalities a short period of vocal rest can be effective. 5. Vocal Fatigue versus Pulmonary Function It was hypothesized that an inverse relationship between PFT values and vocal fatigue would occur. Individuals with lower PFT results would have greater vocal fatigue after a long vocal loading task compared to individuals with higher PFT results. The only PFT measure that indicated statistical significance (p < 0.05) when compared to selfreported vocal fatigue was predicted lung age. Lung age has been proposed as a 36

48 comprehensive indicator for respiratory function (Okamura et al., 06). Equations used to calculate lung age vary, but they take into account FEV values compared to predicted values of FEV based on norms for healthy individuals and include personal information such as age, height, gender and race (Morris & Temple, 985). For example, Toda et al. (009) used the equation Lung age = (0.0 height (cm) fev (L))/0.0 for Japanese females. Usually, it appears, that predicted lung age has been used as physiological tool to promote smoking cessation in smokers by demonstrating their current lung function (Parkes et al., 008). Yet within the current experiment all participants were of self-reported normal respiratory health and indicated that they had no history of smoking or were current smokers. The correlation between vocal fatigue and predicted lung age over time was also apparent with an increased slope observed when participants with older lung ages were compared to participants with younger lung ages. So, potentially, it could be hypothesized that other factors in an individuals environment may be contributing to FEV function, rather than the typically used pulmonary disease, thus affecting predicted lung age. Another option is that predicted lung age is a more comprehensive measure of lung function, which comes into affect when investigating the correlation with vocal fatigue. These results are interesting as predicted lung age is a measure with very limited use in pulmonary function research and essentially no investigation in relation to vocal fatigue. Further research is clearly warranted based on preliminary results and could provide implications for PFTs as a screening tool to assess individuals with a higher risk for vocal fatigue. The potential for PFT measures, specifically lung age, to demonstrate a relationship with other voice disorders, diagnoses or severity, should be considered as well. 37

49 5.3 Acoustic Measures versus Pulmonary Function Acoustic measures of ΔSPL and f 0 were collected from vocal tasks during D and D. They were compared against the same pulmonary function results as vocal fatigue ratings. In this case, the only relationships observed to be approaching statistical significance (p < 0.) were PEF and lung age when compared to f 0. ΔSPL did not show relationships with any pulmonary function measures. While this study indicated, direct correlation of ΔSPL and f 0 to pulmonary function results may not be the most successful indicator of vocal fatigue it is possible that other acoustic measures may have a stronger relationship. Measures of jitter and shimmer have also shown some relationship to vocal fatigue (Laukkanen et al., 008) and could be used in the future to investigate correlation with PFT measures. 5.4 Vocal Fatigue versus Acoustic Measures Previous literature has investigated acoustic measures in conjunction with vocal fatigue. Increases in ΔSPL and a higher f 0, greater activity in the laryngeal muscles, have both been noted as acoustic characteristics that might relate to vocal fatigue (Schloneger & Hunter, 07). Results found within this research generally matched the trends for these two measures already established. The ΔSPL compared to time demonstrated a statistically significant relationship (p<0.05) during the non-fatiguing subjective task of D. Interestingly in the nonfatiguing task the two factors demonstrated a positive linear relationship. This is contradictory to what would have been expected from previous research and results within the study that showed a strong negative correlation between time and subjective 38

50 vocal fatigue ratings. In the non-fatiguing task of Day, f 0 compared to time did show a linear relationship as well but was not statistically significant nor was f 0 compared to selfreported vocal fatigue. Anxiety at the start of the study could have increased ratings and pitch initially with the participants relaxing over the 30-minute time period would echo the slope of the line in Figure 7. The ΔSPL compared to self-reported vocal fatigue did not demonstrate a relationship in the non-fatiguing task of D. This is consistent with previous research, as participants were not undergoing vocal fatigue during the D nonfatiguing task, which was proven in self-reported measures compared to time. In the subjective fatiguing task of D, there was a statistically significant quadratic relationship (p < 0.00) between ΔSPL and time. The results here generally matched previous research, which verify the correlational relationship between these two factors. The greatest ΔSPL occurred at approximately 0 minutes into the fatiguing task. In the fatiguing task of D, f 0 compared to time did show a statistically significant quadratic relationship (p < 0.00). The ΔSPL and f 0 compared to self-reported vocal fatigue in the fatiguing task of D presented a statistically significant quadratic relationship (p < 0.00). The greatest ΔSPL and f 0 occurred at a subjective rating of approximately 6 on a 0-0 scale. Looking at ΔSPL and f 0 compared to time and self-reported vocal fatigue the trends are similar. Specifically in the graphs of D, quadratic curves showing ΔSPL and f 0 compared to time appear to mirror each other with the greatest change in both measures occurring within the first 0 minutes. This may lead to possible implications supporting a shortened experimental time, 0 minutes, in research studies to estimate factors associated vocal fatigue. The setup of the lingwaves program could possibly 39

51 have acted as a contributing factor to the time where an increase of vocal fatigue has been observed. Participant s response to lingwaves cueing to maintain set SPL goals through cycles does correspond with the 0-minute time point, which could be incidental or correlated. The lingwaves system protocol may also have impacted the measure of f 0, although not entirely, since an increased pitch in participant s voices may have been needed to read at a raised level. Additionally, participant s psychological perception of their vocal fatigue changes (i.e. effort, discomfort, tiredness) may have reached a plateau after initially increasing. Another hypothesis is that the cyclic model as proposed by McCabe and Titze (00) could be supported by the results of this particular vocal fatigue study. Changes in the neuromuscular tissue and soft tissues, such as increased vocal fold stiffness, described in the model may result around the time point of 0 minutes resulting in a plateau of the ΔSPL, f 0 and self-reported vocal fatigue levels. Neuromuscular changes described in the model may result around the time point of 0 minutes resulting in a plateau of the ΔSPL, f 0 and self-reported vocal fatigue levels. However, a possible question may be whether sustaining vocal fatigue over an even longer period of time would continue to show a decreased in ΔSPL, f 0 and self-reported vocal fatigue or a plateau. Additionally the graphs of D, the quadratic curves showing ΔSPL and f 0 compared to self-reported vocal fatigue appear to mirror each other as well. The vertex of each parabola occurs at approximately the same location, a 6 on a 0-0 scale. The change in acoustic measures of ΔSPL and f 0 was compared to pre and post vocal tasks (Diapix and Rainbow Passage) in D and D. In D, ΔSPL compared to pre and post tasks was determined to be statistically significant as was D when f 0 was 40

52 compared to pre and post tasks. While the variation in ΔSPL and f 0 is still present in pre and post vocal tasks (Diapix and Rainbow Passage it was not to the degree that occurred during the fatiguing task. This indicates that acoustic measures obtained during a fatiguing task may be a more accurate representation than pre and post measures. Participants completing the vocal tasks pre and post may have become fatigued during the vocal tasks, which could have added to the change in acoustic measurements. Of the two acoustic measures conducted pre and post task, f 0 showed a greater change in the slope of the lines from D to D. 4

53 CHAPTER 6: LIMITATIONS AND FUTURE DIRECTIONS Looking ahead to continuation of this experiment, some changes and improvements could be made to provide increased insight into the results. First, ideally, a greater number of participants would be included in the sample size to enhance the magnitude of the study and thus provide a more accurate sampling of the population. Within that increased sample size, it could be assumed that a larger variation in lung function (or predicted lung age) would be observed contributing to results with broader implications. As justified by the recent findings, a more frequent sampling of participant s subjective ratings of vocal fatigue throughout the non-fatiguing and fatiguing tasks could be included. This would be collected to gain greater understanding into the potential relationship between correlation of timing and vocal fatigue. Furthermore, the limitation of subjective ratings is, of course, that they are variable. Numerous uncontrollable factors in the study could have potentially affected participant s self-reported ratings of vocal fatigue. Even participants awareness that they were undergoing a fatiguing task could have impacted their results, however this is not believed to be the major effect contributing to their subjective ratings. Self-reported vocal fatigue ratings have been used previously in studies showing increased vocal fatigue after a vocal loading task (Chang, 004; Vintturi, Alku, Sala, Sihvo, & Vilkman, 003). Other studies (Solomon et al., 003; Welham & Maclagan, 004) have not supported this effect, hence continued investigation into the validity of this measures is necessitated. In the future, modifying a vocal fatiguing task to fit each individual subject may provide a more realistic experience of vocal fatigue. Individuals speak with a preferred 4

54 vocal intensity, which is considered their baseline. In an attempt to fatigue each participant equally, a measure of their baseline intensity could be collected and then adjusted. For example, a participant who spoke at a higher vocal intensity initially would be required to speak at higher levels to induce vocal fatigue. Alternatively, the distance of the microphone from the participant within the vocal fatiguing task could be adjusted to compensate for various levels of vocal intensity. Various other subsets of the population could be studied using the same or a similar outline of experimental measures to allow for comparison and a collective sampling of the entire population upon completion of various subsets. Some potential populations could include: males, individuals within occupations requiring intensive voice use (i.e. teachers, call center workers, speech-language pathologists) and individuals diagnosed with pulmonary function disorders (i.e. chronic obstructive pulmonary disease, asthma, bronchitis, etc.) Currently being investigated is the relationship vocal fatigue and pulmonary function in geriatric individuals as direct continuation of this research. 43

55 CHAPTER 7: CONCLUSIONS As stated in previous research, the multifaceted problem of vocal fatigue has many varying biological and physiological components. This research investigated breath support and lung function as possible contributing factors. Specifically, the experiment studied the female population who make up a large portion of occupational voice users diagnosed with vocal fatigue. The two-day study was conducted in order to gain insight into the possible relationship between vocal fatigue metrics and PFT results. Results showed a relationship between lung age and subjective vocal fatigue ratings. Throughout the study time also had a statistically significant affect when compared with other variables. For acoustic measures of variations in ΔSPL and f 0 compared to subjective vocal fatigue ratings and time there was shown to be steady increase until approximately 0 minutes into the fatiguing task. This may be attributed to participant s responses to the lingwaves program, participant s perceptions of their psychological and physiological fatigue or increased vocal fold stiffness. Additionally, acoustic measures of variations in ΔSPL and f 0 demonstrated to act as more accurate measures of vocal fatigue when assessed within a vocal loading task. Clinical implications of the results of the study can be expanded across the spectrum of disorders and treatments in the field of speech language pathology. For individuals with voice disorders decreased breath support could contribute to increased dysphonia. For this population, PFTs could act a simple tool to measure lung function. As a method to return to baseline function for a portion voice disorder diagnoses has not yet been identified, targeting breath support may be effective treatment tool to improve an individual s current voicing. Another voice treatment method commonly used clinically 44

56 is the Lee Silverman Voice Treatment (LSVT) which is a program directed towards speech disorders associated with Parkinson s disease. This technique works on increasing vocal intensity from an individual s baseline thus exaggerating the voice. Simultaneously, this act could also be enhancing lung function, possibly improving their measure of predicted lung age. Furthermore, the finding of subjective and acoustic measures of vocal fatigue reaching a plateau at the 0-minute time point could trigger the inquiry for setting a minimum or maximum time for this treatment. Extending beyond LSVT, 0-minutes may be the ideal time point for the onset of vocal fatigue so it could be implicated as a landmark to use, to watch or to a measure patient s status over time. Motor speech disorders are impacted by the inability to plan, program, control or coordinate airflow to execute speech and another area that the results of the study may be applied. PFTs, specifically looking at the measure of predicted lung age, may be a method to test the presence of these disorders or as an objective measure to assess the severity of an individual s disorder. If decreased functioning is observed in PFT measures, quantifiable results showing improvement from clinical treatment, in the form of improved pulmonary function measures, could aid in treatment justification. This is just a sampling of the implications for clinical application in diagnosis and treatment that are generated from the results of this study. One approach for additional investigation into vocal fatigue would be to account for an individual s baseline vocal intensity in a fatiguing task. This could potentially result in a more equal standard of vocal load placed upon each participant. Furthermore, a more frequent sampling of self-reported vocal fatigue reports within a fatiguing task could provide a more precise point where participants reached a plateau in subjective and 45

57 acoustic measurements. Continued research into the relationship between pulmonary function and vocal fatigue in a wider variety of populations is also warranted. 46

58 APPENDICES 47

59 APPENDIX A. Consent Form 48

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